There exist numerous fixing arrangements, in particular mechanical and electromechanical fixing arrangements, intended to prevent, or failing that, to damp either vibration of the devices that they fix together, or vibration that is produced at the device or at the supports therefor and that can be transmitted from the devices to the supports or vice versa.
Certain types of vibration can disturb and sometimes damage the devices and/or the supports that they affect, in particular when they give rise to resonance phenomena. Thus, for example, there is a major risk of a planar satellite antenna structure being destroyed by resonance on launching the spacecraft serving to put it into orbit, when a low-frequency vibration is transmitted to it via its support and/or acoustically.
To avoid such drawbacks, attempts are made firstly to apply treatment directly by damping at the device that needs to be protected against the vibration, and secondly to decouple the vibration source(s) from the device to be protected.
One conventional solution for providing such decoupling consists in interposing passive damping means, such as elastomer washers between a device and its support. Unfortunately, although that solution is very effective against high-frequency and medium-frequency vibration, it suffers from the drawback of tending to amplify the movements caused by vibration whose frequency is low. When the vibration is at frequencies distributed over a wide band, it is then necessary to associate the passive damping means with non-linear displacement-limiting means and/or active control means.
It is known that piezoelectric materials such as PZT or PVDF can be used in passive vibration-damping arrangements.
It is also known that a piezoelectric element having electrodes shunted by an inductive circuit behaves as if it were viscoelastic and it then has a damping factor that is similar to the damping factors of viscoelastic materials and that varies as a function of frequency and as a function of the electrical characteristics of the shunt circuit for a given element.
Document EP-A-0 375 370 describes a method of conditioning a piezoelectric element. That method makes it possible to cause the stiffness of the element to vary significantly by acting on a capacitor included in a resistive circuit via which electrodes provided in the element are shunted. It recommends implementing that method in damping arrangements. However, the damping factor that can be obtained for a piezoelectric element working in bending is considerably lower than the damping factor that can be obtained with elements made of viscoelastic materials.
That method does not make it possible to implement a fixing arrangement that offers both high rigidity and a good damping factor for fixing a device to a support when the device needs to be protected from vibration.